Optical, magnetic and magneto-optic media are primary sources of high performance storage technology which enables high storage capacity coupled with a reasonable price per megabyte of storage. Use of optical media has become widespread in audio, video, and computer data applications in such formats as compact disk (CD), digital versatile disk (DVD) including multi-layer structures like DVD-5, DVD-9, and multi-sided formats such as DVD-10, and DVD-18, magneto-optical disk (MO), and other write-once and re-writable formats such as CD-R, CD-RW, DVD-R, DVDxe2x88x92RW, DVD+RW, DVD-RAM, and the like, hereinafter collectively xe2x80x9cdata storage mediaxe2x80x9d. In these formats, data are encoded onto a substrate into a digital data series. In pre-recorded media, such as CD, the data are typically pits and grooves formed on the surface of a plastic substrate through a method such as injection molding, stamping or the like.
In recordable media, the data are encoded by laser, which illuminates an active data layer that undergoes a phase change, thus producing a series of highly-reflecting or non-reflective regions making up the data stream. In these formats, a laser beam first travels through a plastic substrate before reaching the data layer. At the data layer, the beam is either reflected or not, in accordance with the encoded data. The laser light then travels back through the plastic and into an optical detector system where the data are interpreted.
In some applications, it is desirable to have a limited life for an optical disc. For example, sample computer programs are provided to potential customers in order to entice them to purchase the software. The programs are intended to be used for a limited period of time. Additionally, music and movies are currently rented for a limited time period. In each of these applications and others, when that time has expired, the disc must be returned. A need exists for machine-readable optical discs that do not need to be returned at the end of a rental period. Limited-play discs provide a solution to this problem.
Limited play discs have been produced in various fashions. One method comprised forming a disc where the reflective layer is protected with a porous layer such that the reflective layer becomes oxidized over a pre-determined period of time. Once the reflective layer attains a certain level of oxidation, the disc is no longer readable. The problem with this and other limited play techniques is that these techniques are defeatable.
If the method for providing limited play to optical discs can be easily defeated by a customer or a cottage industry, discs would no longer be xe2x80x9climited-playxe2x80x9d. In the case of a coating or material rendering an optical disc unplayable, for example, facile removal or modification of that coating and/or material could provide a disc with unlimited playability.
There is a great desire on the part of movie studios to protect their intellectual property. Commercialization of limited-play data storage media that can be easily defeated to afford data storage media with unlimited playability would present an unacceptable risk of losing intellectual property.
The present disclosure relates to a limited play optical storage media and a method for limiting access to data thereon. This storage media comprises: an optically transparent substrate; a reflective layer; a data storage layer disposed between said substrate and said reflective layer; an oxygen penetrable UV coating disposed on a side of said substrate opposite said data storage layer; and a reactive layer disposed between said UV coating and said substrate, wherein said optical storage media has an initial percent reflectivity of about 50% or greater and a subsequent percent reflectivity of about 45% or less.
The method for limiting access to data disposed on the data storage media, comprises: directing a light toward at least a portion of said data storage media, wherein at least a portion of said light passes through a UV coating, a reactive layer, a substrate, and a data storage layer; reflecting at least a portion of said light back through said substrate, said reactive layer, and said UV coating; and reducing the percent reflectivity of data storage media to less than about 45%.